In terms of dry fire, I was always (and pretty much remain) of the opinion dry firing a quality centerfire pistol (rimfires are a different story) would have no major negative effect, except perhaps having the firing pin break somewhere way down the line.
I was in a reputable shop not long ago looking at a 245 and the gentleman behind the counter commented when I dry fired the pistol a couple of times. He reported that he had sent a SIG back to the factory for repair (a 229 .40 IIRC). He was reportedly informed by someone at SIG that part of the problem was the wear on the firing pin and I believe the transverse pin that runs crosswise thru the slide. The rep apparently indicated dry firing lead to this type of wear. Of course, the guy had been hand loading his .40 to max power levels for some form of competition (steel plates or bowling pins, I can't recall), which would have likely contributed to this situation more than the dry firing, or so it would seem. In any event, it is all third hand info, however the guy was fairly clean cut fellow running a decent shop and seem fairly knowledgeable about the business, plus he had no particular reason to lie to me at that point anyhow. Just thought I would pass this along on the off chance someone may have heard something similar. But this is the ONLY person that I have ever heard make such a claim. The only reason I gave it even a moment of consideration is for the above reasons. However, until I hear it personally from the SIG rep, I will continue to dry fire. I do use snap caps however.
WOW, the reply from Sig sounds unusual. As you said it would be the heavy loads that would so the damage, not the dry firing.
I was talking to a Sig Rep who is a friend of mine recently and according to him there is absolutely no problem with dry firing without a snap cap. In fact he teaches people to dry fire their weapon atleast 200 times a week to practice trigger control, as he does himself.
Just got off the phone with my brother-inlaw who is a Detective. He told me he wore out 3 firing pin retaining bars "pins" and was advised by the ammorer to use snap caps. He also uses +P ammo so maybe the wear came from that, who knows.
Dry firing can really improve your grouping at the range. I dry fire my 226 and 239, and it helps significantly with my accuracy. However, there's nothin like rackin one in the pipe and lettin it loose. If only .357 ammo wasn't so expensive, I'd do more live fire, but dry fire will help your trigger control.
A simple solution for any gun with an external hammer. Buy a piece of 3/8" rubber tubing. Cut off a piece about 3/8" long. Wedge it into the slot on the slide or frame ahead of the firing pin. Dry fire all you want to. The rubber will cushion the hammer and the firing pin will not move at all (or at least not enough to hurt anything.)
PS When you go to the range and experience FTF, remove the piece of rubber tube!